Download Species At Risk Fact Sheet

 Nearctula sp. 1
Species At Risk Fact Sheet - Nearctula sp. 1
Camosun College, ENVR244
Miles Wang and Dongjian Sun
March 20, 2014
cover photo credit: (2010) Andy Teucher, B.C. Conservation Data Centre Image[1]
Nearctula sp. 1
1. Name and classification
English name: Threaded Vertigo
Scientific name: Nearctula sp. 1
Scientific Name Synonyms: Nearctula rowellii [1]
Classification of taxonomy: [2]
Kingdom
Animalia
Phylum
Mollusca
Class
Gastropoda
Order
Stylommatophora
Family
Pupillidae
Genus
Nearctula
2. Wildlife species description and identification tips
With its uniquely small size, it is nowhere near easy to spot a Threaded Vertigo around
its habitat. This land snail has a high, subcylindrical shell about 2.4-3.3 mm high. The
shell has an ovate shape and a blunt apex with close, thread-like riblets and overall
presents a coarse surface texture. The shell appears to be a dull, dark brown color and
its body appears to be dark grey[3,4].
The most distinguishing feature of Threaded Vertigo is the structure of its aperture( the
opening of the shell, see Fig. 1). The apertural lip is thin and flared[1]. There are four
white denticles, which are tooth-like protuberances, within the aperture. And the broad,
slightly twisted parietal denticle(see Fig.1) is the most prominent. However, the
denticles are only present in adult mature shells[3].
Nearctula sp. 1
Fig 1. Shell of the Threaded Vertigo, showing the arrangement of apertural denticles.
Photo credit: Robert Forsyth. [3]
3. Significance of species
The social and economic significance of Threaded Vertigo is not yet known. Nor has it
received any attention culturally from Aboriginal communities. Nevertheless, it is certain
that this species contributes to the great biodiversity of the arboreal forest communities
supported by large Big Leaf Maples and epiphytic mosses, liverworts, lichens, ferns and
other vascular plants that grow on top, which in turn provide ideal habitat for Threaded
Vertigo and other snail species[3].
4. Distribution
Globally, Threaded Vertigo is only found along the Pacific coast in North America from
southwestern British Columbia southward through western Washington and Oregon to
central California. In Canada, the species occurs only in British Columbia, more
specifically, on Vancouver Island, Gulf Islands, and the Sunshine Coast on the
mainland[1].
Locally, on Vancouver Island, this species has appeared at several sites within the
Greater Victoria Area, including two federal properties (military facilities that operate
under the Department of National Defence) and two regional parks, as well as scattered
sites along the east coast of the island, from Victoria northward to Courtenay. It also
appears in the Gulf Islands National Park on Saturna Island[3].
Fig 2. Canadian distribution of the Threaded Vertigo in southwestern British Columbia
Nearctula sp. 1
(mark in red dots). [1]
5. Habitat
This species is entirely arboreal, or nearly so[4]. In British Columbia, the snails occur in
moist deciduous and deciduous / coniferous mixed wood forests at low elevations,
usually below 200 m[1,5]. They are often associated with Big Leaf Maples and an
understory of ferns and shrubs characteristic of moist, rich sites, especially with older
riparian forests containing large maples[3]. This species is most frequently found on
trunks of maples, and occasionally found on other deciduous trees, on fern fronds, or on
the ground within the leaf litter[3].
6. Life history
Like most pulmonate gastropods, Threaded Vertigo is hermaphroditic (possesses both
male and female reproductive organs) but probably exchanges gametes with other
individuals through copulation. Cross fertilization happens at certain life stage of
Threaded Vertigo, as is to most terrestrial gastropods. The life cycle and survival pattern
of this species still remains largely unknown. In British Columbia, most records of its
occurrences are from fall, but adults of Threaded Vertigo have been spotted in spring
and early summer, suggesting its lifespan may be longer than one year. It is also
hypothesized that these snails hibernate in winter and aestivate during dry periods in
summer[3].
7. Why this species is at risk
In southwest British Columbia, the coastal low elevation areas that Threaded Vertigo
prefers are also ideal for human activities, therefore are often highly developed and
heavily populated. With ever-growing human population and increased human
presence, the habitats of Threaded Vertigo have been constantly threatened by human
activities, which include but not limited to housing developments, agriculture, forestry,
road / infrastructure construction. Habitats of Threaded Vertigo has been shrinking and
fragmented. Even on protected public land, intensive recreational and other uses, as
well as introduced plants and animals still pose significant challenge for Threaded
Vertigo and other land snails.
On the other hand, snail populations are also suffering from adverse effects of climate
change, which not only accelerates habitat fragmentation and degradation, but also has
negative impacts on its life cycle. For example, as a species living in moist conditions,
drier conditions during its activity period from spring to fall would certainly affect its
activities. This will become quite obvious for the populations living at the northern
extremity of the species’ range in British Columbia where the growing season is already
relatively short. Additionally, increased frequency and severity of natural disasters such
as flood and fire events would also be detrimental to snails and their habitats.[3]
Nearctula sp. 1
8. Species status and ranks
According to NatureServe[2], The species is on the British Columbia provincial red list of
species at risk. On April 25, 2010, the Committee on the Status of Endangered Wildlife
in Canada (COSEWIC) designated Threaded Vertigo as "Special Concern" . Schedule 1
of Canadian Species at Risk Act (SARA) also listed Threaded Vertigo as Special
Concern on June 20, 2012.
The species is listed as “apparently secure” globally (G3G5; rounded status G4) with
national status in the United States also “apparently secure” (N3N5) but “imperilled” in
Canada (N2) and British Columbia (S2).
9. Protection
As stated in Section 7, the major challenges facing Threaded Vertigo are habitat loss,
invasive species, natural disasters and climate change. So far in Canada, other than the
designation by COSEWIC and SARA, no actual action is being taken in order to protect
this species. The habitats on public lands are still relatively intact and under no
immediate pressure from development. But these sites are not necessarily safe from
invasive species and habitat degradation caused by climate change as well as
recreational or other uses. The species and habitats on private lands, however, receive
no protection at the moment.[3]
Currently there is no recovery plan for Threaded Vertigo either from the province of
British Columbia or the federal government of Canada (under SARA). Fortunately, by
referring to the existing recovery plan for other gastropod species a strategy may
become clear. In the case of Oregon Forestsnail (Allogona townsendiana), the recovery
objectives are:
(1) To identify and prioritize important habitat throughout the species’ range in B.C.
(2) To secure protection for habitats within the species’ range.
(3) To assess and reduce threats at all known sites in B.C.
(4) To address knowledge gaps (e.g., population ecology, habitat associations,
dispersal) that currently prevents quantitative population and distribution objectives from
being established.
In this document, some notable measures include habitat protection and private land
stewardship, habitat survey and inventory, revising and enforcing relevant laws and
regulations, inter-agency co-operations, identification and reduction of anthropogenic
threats, prevention and control of invasive species, public education and so forth.
References
[1] B.C. Conservation Data Centre. 2014. BC Species and Ecosystems Explorer. B.C.
Minist. of Environ. Victoria, B.C. http://a100.gov.bc.ca/pub/eswp/ Last access: Mar 20,
2014.
Nearctula sp. 1
[2] NatureServe Explorer website. http://explorer.natureserve.org/index.htm
Last access: March 20, 2014
[3] K. Ovaska and L. Sopuck, COSEWIC Assessment and Status Report on the
Threaded Vertigo Nearctula sp. in Canada – 2010. Species at Risk Public Registry,
Environment Canada. http://registrelep-sararegistry.gc.ca/default.asp?lang=En&n=
AAE23336-1. Last Access: March 20, 2014
[4] R. Forsyth, Threaded Vertigo introduction page, E-Fauna BC: Electronic Atlas of the
Fauna of British Columbia [efauna.bc.ca]. Lab for Advanced Spatial Analysis,
Department of Geography, University of British Columbia, Vancouver. Last Access:
March 20, 2014.
[5] Forsyth, R.G. 2004. Land Snails of British Columbia. Royal British Columbia
Museum Handbook. Royal British Columbia Museum, Victoria, B.C.188 pp.
[6] Oregon Forestsnail Recovery Team. 2012. Recovery plan for Oregon Forestsnail
(Allogona townsendiana) in British Columbia. Prepared for the B.C. Ministry of
Environment, Victoria, BC. 50 pp.